OFFSET
0,2
COMMENTS
For a guide to related sequences, see A211795.
LINKS
Index entries for linear recurrences with constant coefficients, signature (4,-5,0,5,-4,1).
FORMULA
a(n)=4*a(n-1)-5*a(n-2)+5*a(n-4)-4*a(n-5)+a(n-6).
G.f.: -x*(8+21*x+12*x^2+x^3) / ( (1+x)*(x-1)^5 ).
MATHEMATICA
t = Compile[{{n, _Integer}},
Module[{s = 0}, (Do[
If[(w < # || x > # || y > # || z > #) &[
Max[w, x, y, z] - Min[w, x, y, z]], s++], {w, 0, n},
{x, 0, n}, {y, 0, n}, {z, 0, n}]; s)]];
Map[t[#] &, Range[0, 40]] (* A212754 *)
(* Peter J. C. Moses, May 24 2012 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, May 28 2012
STATUS
approved